All med schools have the AAA requirement or above for A-levels, but a few such as Cambridge place extra importance on AS results.
As mentioned above, it's really the UKCAT/ BMAT which helps those with lower GCSEs. Off the top of my head, you would be aiming to avoid Cardiff and probably Nottingham, but could have a shot at Newcastle/ Durham, maybe Plymouth.
Look at the individual med school sites for the most up-to-date information.